After reading the thread http://communities.ptc.com/thread/37395, I think the best solution for me is:
use the Input matrix, select which location to consider (or make a loop) use the functions readprn, writeprn and appendprn to get the results back in the mathcad sheet.
This is how lucmeeks discripes it in thread 37395:
've come across this as well. Here's my solution and, not to surprise, it's been suggested above already:
1. make sure that each result is in the form of a single matrix row. (I've no experience with row elements being other than scalar, but I'm pretty sure that strings as elements are allowed too, not sure about about vectors or matrices)
2. Write the result of the first pass with WRITEPRN
3. Write the result of each subsequent pass with APPENPRN. If you try to append a row of different size, you'll get an error.
4. Now you can read in the datafile with READPRN, you should get a matrix with as many columns as there are elements in your original rows, and as many rows as there are passes saved.
5. Process this matrix as you like.
Do you guys agree with me? I think it is the best solution.